: It should work, although an air pressure tank is supposed to be ASME rated, because of the danger in the event of a rupture.

: : Hello, I replaced my 20 year old 40G gas water heater. The old one was not leaking, I just wanted something more efficient. I would like to use the old tank as a pressure tank for a compressor I am building. I have the pump which is currently attached to a 10 gallon tank but would like to upgrade to a 40 gallon tank. An old water heater tank seems like it will work. I removed the outer jacket and insulation from the steel tank. I would be pumping air into this tank to a maximum pressure of 110 PSI. Since a T&P valve is rated higher that that, I figured that my project would work. Do you have any thoughts or suggestions on my idea? : : Thanks,

: : Delta

The pressure that your hot water tanks is rated at is about 30 psig. After 20 years you have not idea what condition the tank is in. I think you'll find the tank will repture or explode. NOT a good idea.